Mark A. Johnson
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View article: Dynamics of Protonated Oxalate from Machine-Learned Simulations and Experiment: Infrared Signatures, Proton Transfer Dynamics and Tunneling Splittings
Dynamics of Protonated Oxalate from Machine-Learned Simulations and Experiment: Infrared Signatures, Proton Transfer Dynamics and Tunneling Splittings Open
The infrared spectroscopy and proton transfer dynamics together with the associated tunneling splittings for H/D-transfer in oxalate are investigated using a machine learning-based potential energy surface (PES) of CCSD(T) quality, calibra…
View article: The Onset for Vibrationally Induced, Intramolecular Proton Transfer at Three Water Molecules in Microhydrated 4-Aminobenzoic Acid
The Onset for Vibrationally Induced, Intramolecular Proton Transfer at Three Water Molecules in Microhydrated 4-Aminobenzoic Acid Open
Protonation of 4-aminobenzoic acid occurs at either the amino group (the N-protomer, N) or at the carboxylic acid C═O group (the O-protomer or O). N lies higher in energy than O in the isolated ion but becomes the more stable of the 4ABAH+…
View article: Mechanism of a Halogen Exchange Reaction in Water: Catalysis by Aqueous Media
Mechanism of a Halogen Exchange Reaction in Water: Catalysis by Aqueous Media Open
Reactions of Cl-, Br-, and I- ions in seawater with incoming molecules from the gas phase are of major atmospheric importance, but their mechanisms are mostly unknown. In this study, using ab initio molecular dynamics (AIMD) simulations, t…
View article: Dynamics of protonated oxalate from machine-learned simulations and experiment: infrared signatures, proton transfer dynamics and tunneling splittings
Dynamics of protonated oxalate from machine-learned simulations and experiment: infrared signatures, proton transfer dynamics and tunneling splittings Open
The infrared spectroscopy and proton transfer dynamics together with the tunneling splittings for H/D-transfer in oxalate are investigated using a machine learning-based potential energy surface (PES) of CCSD(T) quality, calibrated against…
View article: Intramolecular Polarization Contributions to the p<i>K</i><sub>a</sub>’s of Carboxylic Acids Through the Chain Length Dependence of Vibrational Tag-Shifts in Cryogenically Cooled Pyridinium-(CH<sub>2</sub>)<sub><i>n</i></sub>-COOH (<i>n</i> = 1–7) Cations
Intramolecular Polarization Contributions to the p<i>K</i><sub>a</sub>’s of Carboxylic Acids Through the Chain Length Dependence of Vibrational Tag-Shifts in Cryogenically Cooled Pyridinium-(CH<sub>2</sub>)<sub><i>n</i></sub>-COOH (<i>n</i> = 1–7) Cations Open
The pKa's of acids are known to depend on the ionic strength of an electrolyte solution, an effect that qualitatively results from electrostatic interactions of the acid and conjugate base with proximal ions. Here, we explore an intramolec…
View article: Isomer-Specific, Cryogenic Ion Vibrational Spectroscopy Investigation of D<sub>2</sub>- and N<sub>2</sub>-Tagged, Protonated Formic Acid Complexes Using Two-Color, IR-IR Photobleaching
Isomer-Specific, Cryogenic Ion Vibrational Spectroscopy Investigation of D<sub>2</sub>- and N<sub>2</sub>-Tagged, Protonated Formic Acid Complexes Using Two-Color, IR-IR Photobleaching Open
Here we analyze cryogenic ion vibrational spectra of tagged protonated formic acid (PFA) with electronic structure and anharmonic vibrational calculations to establish the isomers generated by electrospray ionization (ESI) followed by buff…
View article: Demonstration of Capture, Cooling, Tagging, and Spectroscopic Characterization of UV Photoproduct Ions in a Cryogenic Ion Trap: Application to 266 nm Photofragment Ions from Rhodamine 6G
Demonstration of Capture, Cooling, Tagging, and Spectroscopic Characterization of UV Photoproduct Ions in a Cryogenic Ion Trap: Application to 266 nm Photofragment Ions from Rhodamine 6G Open
We demonstrate a method to determine the structures of the primary photodissociation products from a cryogenically cooled parent ion. In this approach, a target ion is cooled by a pulse of buffer gas and tagged in a 20 K Paul trap. The col…
View article: A Longitudinal Assessment of Resident and New Graduate Well-Being According to Length of Training: A Report From the Length of Training Pilot in Family Medicine
A Longitudinal Assessment of Resident and New Graduate Well-Being According to Length of Training: A Report From the Length of Training Pilot in Family Medicine Open
Background & Objectives: No prior studies have examined how length of training may influence wellness. As part of the Length of Training Pilot (LoTP), we explored resident and new graduate well-being according to program year and lengt…
View article: Observation of Slow Eigen-Zundel Interconversion in H<sup>+</sup>(H<sub>2</sub>O)<sub>6</sub> Clusters upon Isomer-Selective Vibrational Excitation and Buffer Gas Cooling in a Cryogenic Ion Trap
Observation of Slow Eigen-Zundel Interconversion in H<sup>+</sup>(H<sub>2</sub>O)<sub>6</sub> Clusters upon Isomer-Selective Vibrational Excitation and Buffer Gas Cooling in a Cryogenic Ion Trap Open
The formation of isomers when trapping floppy cluster ions in a temperature-controlled ion trap is a generally observed phenomenon. This involves collisional quenching of the ions initially formed at high temperature by buffer gas cooling …
View article: High-resolution vibrational predissociation spectroscopy of I <sup>−</sup> · H <sub>2</sub> O by single-mode CW infrared excitation in a 3D cryogenic ion trap
High-resolution vibrational predissociation spectroscopy of I <sup>−</sup> · H <sub>2</sub> O by single-mode CW infrared excitation in a 3D cryogenic ion trap Open
We describe the integration of a tunable, single-mode, continuous wave infrared laser into a cryogenic ion spectroscopy experiment to measure the rovibrational spectrum of the I-∙H2O complex in the OH stretching region. These upper levels …
View article: Data Supporting "Effects of Microhydration on the Mechanisms of Hydrolysis and Cl- Substitution in Reactions of N2O5 and Seawater"
Data Supporting "Effects of Microhydration on the Mechanisms of Hydrolysis and Cl- Substitution in Reactions of N2O5 and Seawater" Open
All structures used in paper "Effects of Microhydration on the Mechanisms of Hydrolysis and Cl- Substitution in Reactions of N2O5 and Seawater". See README for more information.
View article: Data Supporting "Effects of Microhydration on the Mechanisms of Hydrolysis and Cl- Substitution in Reactions of N2O5 and Seawater"
Data Supporting "Effects of Microhydration on the Mechanisms of Hydrolysis and Cl- Substitution in Reactions of N2O5 and Seawater" Open
All structures used in paper "Effects of Microhydration on the Mechanisms of Hydrolysis and Cl- Substitution in Reactions of N2O5 and Seawater". See README for more information.
View article: Microhydration of the metastable <i>N</i>-protomer of 4-aminobenzoic acid by condensation at 80 K: H/D exchange without conversion to the more stable <i>O</i>-protomer
Microhydration of the metastable <i>N</i>-protomer of 4-aminobenzoic acid by condensation at 80 K: H/D exchange without conversion to the more stable <i>O</i>-protomer Open
4-aminobenzoic acid (4ABA) is a model scaffold for studying solvent-mediated proton transfer. Although protonation at the carboxylic group (O-protomer) is energetically favored in the gas phase, the N-protomer, where the proton remains on …
View article: Water Network Shape-Dependence of Local Interactions with the Microhydrated −NO<sub>2</sub><sup>–</sup> and −CO<sub>2</sub><sup>–</sup> Anionic Head Groups by Cold Ion Vibrational Spectroscopy
Water Network Shape-Dependence of Local Interactions with the Microhydrated −NO<sub>2</sub><sup>–</sup> and −CO<sub>2</sub><sup>–</sup> Anionic Head Groups by Cold Ion Vibrational Spectroscopy Open
We report the structural evolutions of water networks and solvatochromic response of the CH3NO2- radical anion in the OH and CH stretching regions by analysis of the vibrational spectra displayed by cryogenically cooled CH3NO2-·(H2O)n=1-6 …
View article: Vibrational Signatures of HNO<sub>3</sub> Acidity When Complexed with Microhydrated Alkali Metal Ions, M<sup>+</sup>·(HNO<sub>3</sub>)(H<sub>2</sub>O)<sub><i>n</i>=5</sub> (M = Li, K, Na, Rb, Cs), at 20 K
Vibrational Signatures of HNO<sub>3</sub> Acidity When Complexed with Microhydrated Alkali Metal Ions, M<sup>+</sup>·(HNO<sub>3</sub>)(H<sub>2</sub>O)<sub><i>n</i>=5</sub> (M = Li, K, Na, Rb, Cs), at 20 K Open
The speciation of strong acids like HNO3 under conditions of restricted hydration is an important factor in the rates of chemical reactions at the air-water interface. Here, we explore the trade-offs at play when HNO3 is attached to alkali…
View article: On the Hydrogen Oxalate Binding Motifs onto Dinuclear Cu and Ag Metal Phosphine Complexes
On the Hydrogen Oxalate Binding Motifs onto Dinuclear Cu and Ag Metal Phosphine Complexes Open
We report the binding geometries of the isomers that are formed when the hydrogen oxalate ((CO 2 ) 2 H=HOx) anion attaches to dinuclear coinage metal phosphine complexes of the form [M 1 M 2 dcpm 2 (HOx)] + with M=Cu, Ag and dcpm=bis(dicyc…
View article: Chemical Reduction of Ni<sup>II</sup> Cyclam and Characterization of Isolated Ni<sup>I</sup> Cyclam with Cryogenic Vibrational Spectroscopy and Inert-Gas-Mediated High-Resolution Mass Spectrometry
Chemical Reduction of Ni<sup>II</sup> Cyclam and Characterization of Isolated Ni<sup>I</sup> Cyclam with Cryogenic Vibrational Spectroscopy and Inert-Gas-Mediated High-Resolution Mass Spectrometry Open
NiII cyclam (cyclam = 1,4,8,11-tetraazacyclotetradecane) is an efficient catalyst for the selective reduction of CO2 to CO. A crucial elementary step in the proposed catalytic cycle is the coordination of CO2 to a NiI cyclam intermediate. …
View article: Understanding the electron-water interaction at the molecular level: Integrating theory and experiment in the cluster regime
Understanding the electron-water interaction at the molecular level: Integrating theory and experiment in the cluster regime Open
In this final technical report, we summarize our major accomplishments resulting from a combined experimental-theoretical approach that exploits the unique properties of molecular clusters to elucidate how local interactions at the molecul…
View article: Size-Dependent Onset of Nitric Acid Dissociation in Cs<sup>+</sup>·(HNO<sub>3</sub>)(H<sub>2</sub>O)<sub><i>n</i>=0–11</sub> Clusters at 20 K
Size-Dependent Onset of Nitric Acid Dissociation in Cs<sup>+</sup>·(HNO<sub>3</sub>)(H<sub>2</sub>O)<sub><i>n</i>=0–11</sub> Clusters at 20 K Open
We report the water-mediated charge separation of nitric acid upon incorporation into size-selected Cs+·(HNO3)(H2O)n=0-11 clusters at 20 K. Dramatic spectral changes are observed in the n = 7-9 range that are traced to the formation of man…
View article: Mapping the temperature-dependent and network site-specific onset of spectral diffusion at the surface of a water cluster cage
Mapping the temperature-dependent and network site-specific onset of spectral diffusion at the surface of a water cluster cage Open
Significance Water’s vibrational spectrum is dynamic: The OH oscillator frequency changes spontaneously within a diffuse envelope on an ultrafast timescale. Here, we explore the mechanics that drive this “spectral diffusion” at the molecul…
View article: Characterization of the non-covalent docking motif in the isolated reactant complex of a double proton-coupled electron transfer reaction with cryogenic ion spectroscopy
Characterization of the non-covalent docking motif in the isolated reactant complex of a double proton-coupled electron transfer reaction with cryogenic ion spectroscopy Open
The solution kinetics of a proton-coupled electron transfer reaction involving two-electron oxidation of a Ru compound with concomitant transfer of two protons to a quinone derivative have been interpreted to indicate the formation of a lo…
View article: Evaluation of protonation sites in two MacMillan catalysts in solution by gas phase predissociation spectroscopy and electronic structure calculations
Evaluation of protonation sites in two MacMillan catalysts in solution by gas phase predissociation spectroscopy and electronic structure calculations Open
The protonation sites of first and second generation MacMillan catalyst were evaluated using cryogenic ion vibrational predissociation spectroscopy.The comparison with calculated spectra showed that when isolated in the gas phase, the spec…
View article: Chain Length Dependence of Hydrogen Bond Linkages between Cationic Constituents in Hydroxy-Functionalized Ionic Liquids: Tracking Bulk Behavior to the Molecular Level with Cold Cluster Ion Spectroscopy
Chain Length Dependence of Hydrogen Bond Linkages between Cationic Constituents in Hydroxy-Functionalized Ionic Liquids: Tracking Bulk Behavior to the Molecular Level with Cold Cluster Ion Spectroscopy Open
Hydroxy functionalization of cations in ionic liquids (ILs) can lead to formation of contacts between their OH groups [so-called (c-c) interactions]. One class of these linkages involves cooperatively enhanced hydrogen bonds to anionic par…
View article: Characterization of the alkali metal oxalates (MC<sub>2</sub>O<sub>4</sub><sup>−</sup>) and their formation by CO<sub>2</sub> reduction <i>via</i> the alkali metal carbonites (MCO<sub>2</sub><sup>−</sup>)
Characterization of the alkali metal oxalates (MC<sub>2</sub>O<sub>4</sub><sup>−</sup>) and their formation by CO<sub>2</sub> reduction <i>via</i> the alkali metal carbonites (MCO<sub>2</sub><sup>−</sup>) Open
The reduction of carbon dioxide to oxalate has been studied by experimental Collisionally Induced Dissociation (CID) and vibrational characterization of the alkali metal oxalates, supplemented by theoretical electronic structure calculatio…
View article: Comment on “C–D Vibration at C2 Position of Imidazolium Cation as a Probe of the Ionic Liquid Microenvironment”
Comment on “C–D Vibration at C2 Position of Imidazolium Cation as a Probe of the Ionic Liquid Microenvironment” Open
ADVERTISEMENT RETURN TO ISSUEPREVCommentNEXTComment on "C–D Vibration at C2 Position of Imidazolium Cation as a Probe of the Ionic Liquid Microenvironment"Helen J. ZengHelen J. ZengSterling Chemistry Laboratory, Yale University, New Haven,…
View article: Spectroscopic Assessment of Intra- and Intermolecular Hydrogen Bonding in Ether-Functionalized Imidazolium Ionic Liquids
Spectroscopic Assessment of Intra- and Intermolecular Hydrogen Bonding in Ether-Functionalized Imidazolium Ionic Liquids Open
Functionalization of the imidazolium (Im+) cationic component of ionic liquids (ILs) with ether chains affords the possibility of tuning their properties through manipulation of the resulting interion and intramolecular interactions. Herei…